Determination of Iron in Cements by Zinc Reduction-Potassium Dichromate Titrimetry

Abstract

In the Japanese Industrial Standard method (JIS R 5202) for the determination of iron in cements, it is recommended to use tin (II) chloride as reducing reagent of iron (III) and mercury (II) chloride for the oxidation of the excess tin (II) chloride. The zinc reduction-potassium dichromate titrimetry has been developed in order not to cause enviromental pollution by mercury chloride which is contained in the waste water.
After 1g of cement sample was dissolved in excess hydrochloric acid, 1.0g of zinc powder, which could be found most suitable reducing reagent, was added into the solution. By heating the solution, the zinc powder could be dissolved immediately in excess hydrochloric acid and reduced iron (III) in the solution to iron (II) easily.
Eight kinds of diverse ions such as sodium, potassium, magnesium, calcium, aluminum, silicon, titanium and sulfate, which present in cements, did not show interference.
Analytical results of iron in cements obtained by the proposed method agreed well with those by the JIS method (JIS R 5202). The time of determination was about 30 minutes.